Multi-fuel system and method

ABSTRACT

A method provides for operating an engine configured to use a plurality of differing fuels. The method includes determining a fuel combustion ratio of the plurality of differing fuels associated with at least one engine cylinder of the engine based at least in part on one or more of a plurality of characteristic profiles. This maintains one or more of a plurality of actual values associated with usage of the plurality of differing fuels relative to defined corresponding threshold values. The fuel combustion ratio includes a ratio of the plurality of differing fuels to be delivered to the at least one engine cylinder. A fuel delivery system delivers the plurality of differing fuels to the at least one engine cylinder based on the fuel combustion ratio.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. Non-Provisionalpatent application Ser. No. 14/251,726, entitled “MULTI-FUEL SYSTEM ANDMETHOD,” filed on Apr. 14, 2014 (and to be issued as U.S. Pat. No.9,309,819 on Apr. 12, 2016), which is a continuation-in-part ofInternational Application No. PCT/US2012/064929, entitled “FUELOPTIMIZING SYSTEMS FOR A MOBILE ASSET, AND A RELATED METHOD THEREOF,”filed on Nov. 14, 2012, which is a continuation of U.S. application Ser.No. 13/328,438, entitled, “FUEL OPTIMIZING SYSTEM FOR A MOBILE ASSET,AND A RELATED METHOD THEREOF,” filed on Dec. 16, 2011, now U.S. Pat. No.8,682,512 issued Mar. 25, 2014. This application is also acontinuation-in-part of U.S. Non-Provisional patent application Ser. No.15/013,432, entitled “METHOD FOR OPERATING AN ENGINE,” filed on Feb. 2,2016, which is a continuation-in-part of U.S. Non-Provisional patentapplication Ser. No. 13/484,621, entitled “METHOD FOR OPERATING ANENGINE,” filed on May 31, 2012, now U.S. Pat. No. 9,249,744 issued Feb.2, 2016. The entire contents of each of the above-referencedapplications are hereby incorporated by reference for all purposes.

FIELD

Aspects of the invention relate to a multi-fuel system for engines andan associated method of operation.

BACKGROUND

Some mobile assets may have engines, for example, compression-ignitionengines operate by directly injecting a fuel (e.g., diesel fuel) intocompressed air in one or more piston-cylinder assemblies, such that theheat of the compressed air ignites the fuel-air mixture. The direct fuelinjection atomizes the fuel into droplets, which evaporate and mix withthe compressed air in the combustion chambers of the piston-cylinderassemblies. The fuel-air ratio affects engine performance, efficiency,exhaust constituents, and other engine characteristics. Exhaustemissions may include carbon oxides (e.g., carbon monoxide), nitrogenoxides (NOx), sulfur oxides (SOx), and particulate matter (PM). Theamount and relative proportion of these constituents may vary inresponse to changes in the fuel-air mixture, fuel quality, compressionratio, injection timing, environmental conditions (e.g., atmosphericpressure, temperature, etc.), and so forth.

A dual-fuel engine is an alternative internal combustion engine designedto run on more than one fuel, for example, natural gas and diesel, eachstored in separate vessels. Such engines are capable of burning amixture of the resulting blend of fuels in the combustion chamber andthe fuel injection or spark timing may be adjusted according to theblend of fuels in the combustion chamber. For dual fuel operation whereone of the fuel is premixed with air, a reduction in nitrogen oxide(NOx) and particulate matter (PM) emissions is enabled by combusting arelatively larger fraction of the premixed fuel. It may be desirable tohave a system and method for engines operating on more than one fuelthat differs from those currently available.

BRIEF DESCRIPTION

In accordance with one embodiment, a method is provided for operating anengine configured to use a plurality of differing fuels. The methodincludes determining a fuel combustion ratio of the plurality ofdiffering fuels associated with at least one engine cylinder of theengine based at least in part on one or more of a plurality ofcharacteristic profiles. This is to maintain one or more of a pluralityof actual values associated with usage of the plurality of differingfuels relative to defined corresponding threshold values. The fuelcombustion ratio includes a ratio of the plurality of differing fuels tobe delivered to the at least one engine cylinder. A fuel delivery systemdelivers the plurality of differing fuels to the at least one enginecylinder based on the fuel combustion ratio.

In one embodiment, a fuel system is provided that includes a fuelcontrolling unit. The fuel controlling unit delivers a plurality offuels to at least one engine cylinder of an engine based at least inpart on a fuel combustion ratio. The fuel combustion ratio comprises aratio of the plurality of fuels to be delivered to the at least oneengine cylinder and is based at least in part on one or more of aplurality of characteristic profiles. The fuel controlling unitmaintains one or more of a plurality of actual values associated withusage of the plurality of fuels relative to defined correspondingthreshold values.

In one embodiment, an engine is disposed within a mobile asset operableto travel along a defined path. A global positioning sensor provides,and the fuel controlling unit receives from the global positioningsensor, location information and thereby determines the one or more ofthe plurality of characteristic profiles as a function of time and acorresponding location of the mobile asset along the defined path.

DRAWINGS

These and other features and aspects of the invention may be understoodwhen the following detailed description is read with reference to theaccompanying drawings in which like characters represent like partsthroughout the drawings, wherein:

FIG. 1 is a diagrammatical representation of a mobile asset, for examplea locomotive, having a fuel controlling unit in accordance with anembodiment of the present invention.

FIG. 2 is a diagrammatical representation of a mobile asset withdetailed view of a fuel controlling unit in accordance with anembodiment of the present invention.

FIG. 3 is a flow diagram illustrating exemplary steps involved inoptimization of fuel in a mobile asset in accordance with an embodimentof the present technique.

FIG. 4 is a flow diagram illustrating exemplary steps involved inoptimization of fuel in a mobile asset in accordance with an embodimentof the present technique.

DETAILED DESCRIPTION

In accordance with the embodiments discussed herein, a method and a fuelsystem for use operating an engine using a plurality of fuels isdisclosed. The engine may power or propel a stationary asset or a mobileasset.

A suitable mobile asset can be a vehicle or other engine poweredassembly. Suitable vehicles may include locomotives, passenger andnon-passenger automotive vehicles, hybrid vehicles, off-highwayvehicles, on-road vehicles (such as tractor trailers), tracked vehicles,air-borne vehicles, rail vehicles, mining vehicles, industrial andconstruction vehicles, and marine vessels. Suitable mobile assets mayuse other fuels instead of diesel and natural gas. Other suitable liquidfuels may include gasoline, kerosene, ethanol, bio-diesel, and the like.Other suitable gaseous fuels may include propane, hydrogen, syn-gas, andthe like.

A mobile asset's configuration may include performance variables such asthe peak output rating of the mobile asset, the correlation between thepower level settings and the percentage of full power generated, engineemissions curves, acoustic emissions, electro-magnetic emissions, thenumber of traction motors used, fuel economy performance, adhesionlimits, the organization, presentation and functionality of operatorcontrols, communications protocol, auxiliary functions, securitymeasures, and the like. External factors that can affect the mobileasset's desired configuration can include tax liabilities for operation,weather considerations, damage risk (due to crime or conflict),proximity to population centers, and the like. The control of fuel usagemay be determined with reference to various characteristic profilesassociated with the engine operation and/or mobile asset and may vary asa function of time and a corresponding location of the asset along thepath.

A reduction in nitrogen oxide (NOx) and particulate matter (PM)emissions may be enabled by combusting a relatively larger fraction ofpremixed fuel. Relative costs and availability of different fuels may bein flux. For example, in some embodiments, diesel and natural gas may beutilized to drive the engine. If the cost of diesel increases relativeto the cost of the natural gas, more natural gas may be used resultingin reduced cost and emissions. If the cost of natural gas increasesrelative to the cost of the diesel, then more diesel may be used todrive the engine.

The term “profiles” is used herein to describe the overall operatingparameters and conditions of the engine and/or mobile asset. Theseprofiles may alter the manner in which the operating systems of themobile asset can be controlled in response to operational inputs.

Referring to FIG. 1, a mobile asset 10 moving from a first operatingpoint 12 to a second operating point 14 along a defined path 16 isdisclosed. In the illustrated embodiment, the mobile asset may be drivenby an engine 18 using a plurality of fuels. A fuel controlling unit 20may control fuel utilization based on cost and availability whileensuring emission compliance along the travel from the first operatingpoint to the second operating point along the defined path.

Referring to FIG. 2, the mobile asset includes a turbocharger 22 and thecompression-ignition engine, e.g. the diesel engine. A motor-generatorunit (not shown) may be mechanically coupled to the turbocharger. Asdiscussed in further detail below, embodiments of the technique providemonitoring and control features, such as sensors and control logic, tocontrol/control the utilization of fuel.

The illustrated engine includes an air intake manifold 24 and an exhaustmanifold 26. The turbocharger includes a compressor 28 and a turbine 30and may be operated to supply compressed air to the intake manifold forcombustion within the engine. The turbine may be coupled to the exhaustmanifold for extracting energy from exhaust gases for rotating aturbocharger shaft 32 connected to the compressor. The compressor drawsambient air through a filter 34 and provides compressed air to a heatexchanger 36. The temperature of air may be increased due tocompression. The compressed air flows through the heat exchanger suchthat the temperature of air may be reduced prior to delivery into theintake manifold of the engine. In one embodiment, the heat exchanger maybe an air-to-water heat exchanger, which utilizes a coolant tofacilitate removal of heat from the compressed air. In anotherembodiment, the heat exchanger may be an air-to-air heat exchanger,which utilizes ambient air to facilitate removal of heat from compressedair. The fuel controlling unit may be used for another type of engine ormobile asset using a plurality of fuels so as to control fuelutilization based on cost and availability while ensuring emissioncompliance during travel.

The fuel controlling unit may include a plurality of sensors and acontrol unit 38. Suitable sensors may include one or more of an engineemission level sensor 40, a fuel usage level sensor 42, a power outputsensor 44, an engine load sensor 46, an engine speed sensor 48, fuelcost meter 50, a fuel injection profile sensor 52, a knock sensor (notshown), an oxygen content sensor (not shown), temperature sensors (notshown), pressure sensors (not shown), a valve sensor (not shown), andthe like. A global positioning sensor (GPS) 53 may communicate with thefuel controlling unit.

A suitable control unit may be an electronic fuel injection control unitfor the engine or an electronic logic control unit that may beprogrammable by a user. The control unit may produce a signal to controloperation of a fuel delivery system 41. The fuel delivery system mayhave one or more fuel injection pumps, gas control valves, acommunication path to regasification unit (which, in one embodiment, maybe located on another mobile asset coupled to the mobile asset thatsupports the engine and the fuel controlling unit), a gas recirculationpump, and the like. The fuel injection pumps may provide fuel, underpressure, to a plurality of plurality of fuel injectors (not shown) forinjecting fuel into a cylinder of the engine.

A piston (not shown) may be slidably disposed in each cylinder andreciprocates between a top dead center and a bottom dead centerposition. The control unit may receive an engine emission level signalfrom the level sensor, a fuel usage level signal from the sensor, apower output signal from the power sensor, an engine load signal fromthe load sensor, an engine speed signal from the speed sensor, fuel costfrom the meter, and a fuel injection profile signal from the injectionsensor.

The control unit may receive one or more signals associated with atleast one of a distance from the first operating point to the secondoperating point along the defined path, terrain profile associated withthe path, ambient temperature and pressure, time required to traversethe distance, and location of one or more fuel stations along thedefined path from the GPS unit. The terrain profile can includeinformation relating to the path, such as the grade, the curvature, thealtitude, and the path condition. Path condition can include the stateof repair or wear of the path, for example the condition of rail track.

The control unit may include a memory 54, an algorithm 56, and aprocessor 58. The memory may store information associated with themobile asset, the path, the engine, environmental conditions (such assnow during a winter or leaf cover in the fall), and the like. Thememory may store information relating to average temperatures andpressures associate with either the ambient or of operations of theengine. Other stored information may include maps, tables and modelsrelating to, for example, fuel injection timing and pressure, enginespeed, power output of the engine, engine emission level, fuel usagelevel, engine load, fuel cost, distance from the first operating pointto the second operating point along the defined path, terrain profileassociated with the path, ambient temperature and pressure, timerequired to traverse the distance, and location of one or more fuelstations along the defined path, or the like.

Regarding injection timing, more than diesel fuel is contemplated hereinand the term is used to indicate aspects of fuel flow (both gas andliquid) into the cylinder relative to the combustion cycle. Thus,injection timing information may include a duration that a solenoidopens in the injector to ingress fuel into the cylinder, the pressure ofthe fuel being injected, the timing of the injection relative to thepiston location in the cylinder, and the like. Additionally, injectiontiming may additionally refer to the fumigation or injection of gaseousfuel into the air intake valve for the cylinder. In this aspect,injection timing may refer to the flow rate of the gas, the volume ofEGR in the manifold, the oxygen content (calculated or measured) in themanifold, and the like. Furthermore, the memory may store actualsensed/detected information from the above-mentioned sensors.

The algorithm facilitates the processing of signals from one or more ofthe plurality of sensors. The characteristic profiles associated withthe mobile asset may include the output from the sensors and informationstored in the memory.

The processor may include a range of circuitry types, such as amicroprocessor, a programmable logic controller, a logic module, etc.The processor in combination with the algorithm may perform the variouscomputational operations relating to determination of a combustion ratioof the plurality of fuels to be delivered to at least some cylinders ofthe engine. The combustion ratio is determined by the ratio of theplurality of fuels delivered to cylinders of the engine. For an engineusing diesel and natural gas, a combustion ratio would be ratio ofdiesel content to natural gas content to be delivered to each cylinder.As noted, the diesel content may be measured as an injection time anddiesel pressure through an injector. The natural gas content may bemeasured by a flow rate through a gas valve as metered into an airintake stream. The ratio, then, could be selected as the energy contentof each fuel component present in a cylinder during combustion.Alternatively, other calculations may be used to form the ratio.

The processor may determine the fuel combustion ratio of the pluralityof the fuels associated with each engine cylinder of the mobile assetbased on the plurality of characteristic profiles. In some embodiments,the processor determines the combustion ratio based on the output fromthe sensors 40, 42, 44, 46, 48, 50 and 52. In certain other embodiments,the processor 58 determines the combustion ratio based on the outputfrom the GPS 53. In a specific embodiment, the processor 58 utilizesinformation from the GPS 53 in conjunction with the information from theother sensors 40, 42, 44, 46, 48, 50 and 52 to determine the combustionratio. Additionally, the processor 58 may also use the informationstored in the memory 54.

In the illustrated embodiments, the mobile asset has a first fuel source60 and a second fuel source 62 for feeding a first fuel and a secondfuel respectively, to corresponding cylinders of the engine. The firstand second fuels may be injected to the cylinders via the intakemanifold or may be injected directly to the cylinders, or a combinationof both or other ingress techniques. More than two fuels may be used.

The processor outputs a control signal to the fuel delivery system todeliver the plurality of fuels to the cylinders based on, at leastpartially, the combustion ratio. The combustion ratio may be determinedto maintain a plurality of actual values associated with usage of theplurality of fuels relative to defined corresponding threshold values.In one embodiment, an actual cost associated with usage of the pluralityof fuels may be maintained to less than or equal to a defined thresholdcost; an actual emission level associated with usage of the plurality offuels may be maintained to less than or equal to a defined thresholdemission level; and, an actual quantity of fuel in the mobile asset maybe maintained to less than or equal to a defined threshold quantity. Thefuel controlling unit may control fuel utilization, and the ratio of useof the plural fuels relative to each other, based on cost andavailability while ensuring emission compliance along the entire travelfrom the first operating point to the second operating point along thedefined path. For example, if two fuels are used, the controlling unitmay control a relatively larger usage of a secondary fuel and so thatadequate primary fuel exists to complete the travel, taking intoconsideration the characteristics profiles.

Relative costs, purity, type and availability of different fuels may bein flux. Also, proportions of different fuels may also have an effect onthe exhaust constituents from the engine. In one embodiment, the fuelcontrolling unit takes into consideration sensed engine emission level,a fuel usage level (i.e. quantity of fuel required for the travel,remaining quantity of fuel in the fuel sources 60, 62) the engine poweroutput, the engine load, the engine speed, fuel cost, and the fuelinjection profile. In an embodiment, the fuel controlling unit mayconsider distance from the first operating point to the second operatingpoint along the defined path, terrain profile associated with the path,ambient temperature and pressure, time required to traverse thedistance, and location of one or more fuel stations along the definedpath, or the like. Other suitable parameters may be also envisaged.

Parameters may vary dynamically as a function of time and location ofasset. In accordance with an embodiment, the plurality of characteristicprofiles associated with the mobile asset may be determined as afunction of time and a corresponding location of the mobile asset alongthe defined path. Hence, the fuel controlling unit may also determinethe fuel combustion ratio as a function of time and a correspondinglocation of the mobile asset based on the one or more of the pluralityof characteristic profiles. The frequency of sensing the characteristicsprofiles and determination of the combustion ratio may be based on thetype of application.

In certain embodiments, the control unit may output data to a userinterface 64. The user interface may facilitate inputs via a touchscreen 66 from a user to the control unit and provide a mechanismthrough which a user can manipulate data and sensed properties from thecontrol unit. The user interface may include a command line interface,menu driven interface, and/or graphical user interface. The control unitmay be operable to adjust the combustion ratio affecting the cost andengine emissions associated with the fuel usage. In some embodiments,the control unit may communicate to a user via the user interfacewhether it may be possible to reach a predetermined destination withavailable of fuel(s) in the asset, while meeting emissions targets.

As described above, the control unit may measure a plurality of engineparameters based on output from a variety of sensors, including but notlimited to fuel injection timing sensors, fuel flow sensors, throttleposition sensors, manifold air pressure sensors, manifold airtemperature sensors, exhaust gas temperature sensors, engine powersensors, knock sensors or the like. Thus, in non-limiting examples, themeasured engine parameters may comprise at least one of engine speed,engine load, engine throttle position, intake manifold temperature,intake manifold pressure, exhaust gas flow rate and temperature, airflow into the cylinder, compression ratio, or intake and exhaust valvetiming.

In other embodiments, examples of other engine parameters may comprise astatus of one or more sensors. For example, a measured engine parametermay comprise if a particular sensor (e.g., knock sensor, temperaturesensor, etc.) is broken or not operating correctly.

In still another embodiment, another engine parameter may comprise anaftertreatment status. The aftertreatment status may comprisetemperature, flow, and/or pressure drop of a predetermined quantity,whether the aftertreatment is regenerating, measured engine operationover time, anticipated regeneration start event, estimated collection offlammable substances in the aftertreatment system, and the like.

Referring to FIG. 3, a flow diagram 68 illustrating a plurality of stepsinvolved in optimization of fuel for a mobile asset may be disclosed.Initially, a plurality of characteristic profiles associated with themobile asset moving from one operating point to another operating pointalong a defined path may be determined as represented by the step 70. Inone embodiment, the characteristic profiles may include asset sensedinformation, the characteristics profiles may include GPS information,the characteristics profile may include memory stored information, andthe characteristics profile may be determined as a function of time andlocation of the mobile asset. In one example, the plurality ofcharacteristic profiles comprises one or more of global positioningsensor (GPS) information for the location of the mobile asset, acalculated distance from a current location of the mobile asset to afuel station, a fuel cost for one or more of the plurality of fuels, aterrain profile associated with a location on the defined path, or anambient temperature or ambient pressure proximate to the mobile asset.On an example, the plurality of characteristic profiles may include twoof the above parameters. In an alternate or additional example, theplurality of characteristic profiles comprises at least one asset sensedinformation comprising at least one of an engine emission level, a fuelusage level, a power output, an engine load, an engine speed, or a fuelinjection profile.

Then, a fuel combustion ratio of the plurality of the fuels associatedwith at least one engine cylinder of the mobile asset may be determinedbased on the plurality of characteristic profiles as represented by thestep 72. The fuel combustion ratio refers to a ratio of the plurality offuels to be delivered to the at least one engine cylinder of the mobileasset, and may be determined as a function of time and location of themobile asset.

A fuel delivery system may be controlled based on the determined fuelcombustion ratio as represented by the step 74. The fuel delivery systemdelivers the plurality fuels based on the determined fuel combustionratio as represented by the step 76. As a result, the actual emissionlevel associated with usage of the plurality of fuels may be maintainedto less than or equal to a defined threshold emission level asrepresented by the step 78. For example, a measured exhaust emissionconstituent level may be controlled relative to a defined thresholdemission level. An actual quantity of the plurality of fuels in themobile asset may be maintained less than or equal to a defined thresholdquantity as represented by the step 80. The actual cost associated withusage of the plurality of fuels may be maintained to less than or equalto a defined threshold cost as represented by the step 82.

Referring to FIG. 4, a flow diagram 84 illustrating a plurality of stepsinvolved in optimization of fuel for a mobile asset may be disclosed. Aplurality of engine parameters may be monitored as represented by thestep 86, including measuring the engine parameters via one or moresensors and/or calculating or estimating the engine parameters. Themeasured engine parameters may include engine speed, engine load, enginethrottle position, intake manifold temperature, intake manifoldpressure, exhaust gas flow rate and temperature, air flow into thecylinder, compression ratio, intake and exhaust valve timing, sensorstatus (e.g., knock sensor status), and aftertreatment status.

A plurality of characteristic profiles associated with the mobile assetmoving from one operating point to another operating point along adefined path may be determined as represented by the step 88. In oneembodiment, the characteristic profiles may include asset sensedinformation, the characteristics profiles may include GPS information,the characteristics profile may include memory stored information, andthe characteristics profile may be determined as a function of time andlocation of the mobile asset. In one example, the plurality ofcharacteristic profiles comprises one or more of global positioningsensor (GPS) information for the location of the mobile asset, acalculated distance from a current location of the mobile asset to afuel station, a fuel cost for one or more of the plurality of fuels, aterrain profile associated with a location on the defined path, or anambient temperature or ambient pressure proximate to the mobile asset.In an example, the plurality of characteristic profiles may include twoof the above parameters. In an alternate or additional example, theplurality of characteristic profiles comprises at least one asset sensedinformation comprising at least one of an engine emission level, a fuelusage level, a power output, an engine load, an engine speed, or a fuelinjection profile. In a further example, the plurality of characteristicprofiles may additionally or alternatively comprise one or more ofhistorical operational data or ambient conditions along the definedpath. The historical operational data may include historical fuel usagelevels for the plurality of fuels supplied to the engine in order totraverse the defined path, historical ambient conditions (e.g.,historical pressure and temperature), historical path conditions (e.g.,track wear), and/or other operational data.

Then, a fuel combustion ratio of the plurality of the fuels associatedwith at least one engine cylinder of the mobile asset may be determinedbased on the measured engine parameters and the plurality ofcharacteristic profiles as represented by the step 90. The fuelcombustion ratio refers to a ratio of the plurality of fuels to bedelivered to the at least one engine cylinder of the mobile asset, andmay be determined as a function of time and location of the mobileasset.

A fuel delivery system may be controlled based on the determined fuelcombustion ratio. The fuel delivery system delivers the plurality fuelsbased on the determined fuel combustion ratio as represented by the step92. As a result, the actual emission level associated with usage of theplurality of fuels may be maintained to less than or equal to a definedthreshold emission level as represented by the step 94. An actualquantity of the plurality of fuels in the mobile asset may be maintainedless than or equal to a defined threshold quantity as represented by thestep 96. The actual cost associated with usage of the plurality of fuelsmay be maintained to less than or equal to a defined threshold cost asrepresented by the step 98.

In one example, one of the one or more monitored engine parametersincludes an increased load operation of the engine. The increased loadoperation may include a transient acceleration operation. During thetransient acceleration operation, the fuel combustion ratio may beadjusted to avoid knock, for example. In an example, the quantity of afirst fuel may be reduced and the quantity of the second fuel may beincreased.

In an example, the increased load operation may include or be due to anincreased gradient of the path at the mobile asset current location. Inone example, the control unit may determine in advance that an increasedgradient is coming up along the path and then pre-stage the engine toanticipate the increased load. The pre-staging may include switchinghardware configurations of the engine. The hardware configurations thatmay be switched include one or more of a valve event (e.g., adjustingone or more of timing, lift, or duration of an intake and/or exhaustvalve), compression ratio, piston, piston ring, valve lift profile,pressure sensor, temperature sensor, knock sensor, injector, andinjector nozzle.

In a further example, one of the one or more monitored engine parametersincludes an aftertreatment status where the aftertreatment system maysuffer damage as a result of a sudden increase in temperature beyond alimited temperature (e.g., temperature point, rate of rise, etc.). Thismay be in conjunction with extended idle or cold operation. For example,the status of the aftertreatment may be that the aftertreatment hasaccumulated a large amount of flammable material including oil, unburnedfuel, and/or particulate. Alternatively, the status of theaftertreatment may be that it is at a relatively low temperature andwould suffer from extreme thermal stresses in the event of a suddenincrease in temperature. In this embodiment, the fueling may be adjustedsuch that the temperature of the aftertreatment is controlled to preventdamage.

In an example, one of the one or more monitored engine parametersincludes a sensor status for a temperature sensor or a knock sensor. Forexample, if a particular sensor (e.g., knock sensor, temperature sensor,etc.) is broken or not operating correctly, the fuel combustion ratiomay be adjusted to proactively prevent knocking that might otherwise goundetected.

In an example, one of the one or more monitored engine parametercomprises increased engine speed. During the increased engine speedoperation, the fuel combustion ratio may be adjusted to avoid knock, forexample. In an example, the quantity of a first fuel may be reduced andthe quantity of the second fuel may be increased.

In one embodiment, a method includes determining a plurality ofcharacteristic profiles associated with a mobile asset moving from afirst operating point to a second operating point along a defined path.A fuel combustion ratio is determined for the plurality of the fuelsassociated with at least one engine cylinder of the mobile asset basedon the plurality of characteristic profiles so as to maintain aplurality of actual values associated with usage of the plurality offuels to less than or equal to defined corresponding threshold values.The fuel combustion ratio is a ratio of the plurality of fuels to eachother, and may be calculated in one of several ways depending on theapplication. As used here, suitable determination methods may include bymeasured volume, mass, flow rate, injection time, and the like, and maytake into account purity, energy density, the presence, type andquantify of fuel additives, environmental considerations, EGR content,and the like. A fuel delivery system of the mobile asset may deliver theplurality of fuels to the at least one engine cylinder based on the fuelcombustion ratio.

In an example, a fuel system includes a fuel controlling unit configuredto deliver a plurality of differing fuels to at least one enginecylinder of an engine based at least in part on a fuel combustion ratio,wherein the fuel combustion ratio comprises a ratio of the plurality offuels to be delivered to the at least one engine cylinder and is basedat least in part on one or more of a plurality of characteristicprofiles along a defined path of a mobile asset in which the engine isdisposed, wherein the fuel combustion ratio comprises a ratio of theplurality of fuels to be delivered to the at least one engine cylinder,and the plurality of characteristic profiles comprises one or more ofglobal positioning sensor (GPS) information for the location of themobile asset, a calculated distance from a current location of themobile asset to a fuel station, a fuel cost for one or more of theplurality of fuels, a terrain profile associated with a location on thedefined path, or an ambient temperature or ambient pressure proximate tothe mobile asset.

The system may further comprise one or more sensors operable tocommunicate sensor information with the fuel controlling unit sensorinformation, and the fuel controlling unit may be operable to receivethe sensor information and thereby to determine the one or more of theplurality of characteristic profiles. The fuel controlling unit may beconfigured to signal a fuel demand to a regasification unit to supply atleast one of the plurality of fuels. The fuel controlling unit may beconfigured to maintain an actual quantity of at least one of theplurality of fuels in the mobile asset to less than or equal to adefined threshold quantity for that fuel. The plurality ofcharacteristic profiles may further comprise one or more of historicaloperational data or ambient conditions along the defined path. In anexample, the mobile asset in which the engine is disposed is a vehicle.In an example, the vehicle is a rail vehicle, and the plurality ofdiffering fuels include diesel and natural gas.

As used herein, an element or step recited in the singular and proceededwith the word “a” or “an” should be understood as not excluding pluralof said elements or steps, unless such exclusion is explicitly stated.Furthermore, references to “one embodiment” of the present invention arenot intended to be interpreted as excluding the existence of additionalembodiments that also incorporate the recited features. Moreover, unlessexplicitly stated to the contrary, embodiments “comprising,”“including,” or “having” an element or a plurality of elements having aparticular property may include additional such elements not having thatproperty. The terms “including” and “in which” are used as theplain-language equivalents of the respective terms “comprising” and“wherein.” Moreover, the terms “first,” “second,” and “third,” etc. areused merely as labels, and are not intended to impose numericalrequirements or a particular positional order on their objects.

This written description uses examples to disclose the invention, and toenable a person of ordinary skill in the relevant art to practice theinvention, including making and using any devices or systems andperforming any incorporated methods. The patentable scope of theinvention is defined by the claims, and may include other examples thatoccur to those of ordinary skill in the art. Such other examples areintended to be within the scope of the claims if they have structuralelements that do not differ from the literal language of the claims, orif they include equivalent structural elements with insubstantialdifferences from the literal languages of the claims.

1. A method for operating an engine configured to use a plurality ofdiffering fuels, the method comprising: determining a fuel combustionratio of the plurality of differing fuels associated with at least oneengine cylinder of the engine based at least in part on one or more of aplurality of characteristic profiles along a defined path of a mobileasset in which the engine is disposed, wherein the fuel combustion ratiocomprises a ratio of the plurality of differing fuels to be delivered tothe at least one engine cylinder, and the plurality of characteristicprofiles comprises one or more of global positioning sensor (GPS)information for a current location of the mobile asset, a calculateddistance from the current location of the mobile asset to a fuelstation, a fuel cost for one or more of the plurality of differingfuels, a terrain profile associated with a location on the defined path,or an ambient temperature or ambient pressure proximate to the mobileasset; and controlling a fuel delivery system to deliver the pluralityof differing fuels to the at least one engine cylinder based on thedetermined fuel combustion ratio.
 2. The method of claim 1, where theplurality of characteristic profiles comprises two or more of the GPSinformation for the current location of the mobile asset, the calculateddistance from the current location of the mobile asset to the fuelstation, the fuel cost for one or more of the plurality of differingfuels, the terrain profile associated with the location on the definedpath, or the ambient temperature or ambient pressure proximate to themobile asset.
 3. The method of claim 1, wherein the plurality ofcharacteristic profiles comprises at least one asset sensed informationcomprising at least one of an engine emission level, a fuel usage level,a power output, an engine load, an engine speed, or a fuel injectionprofile.
 4. The method of claim 1, further comprising controlling ameasured exhaust emission constituent level relative to a definedthreshold emission level.
 5. A method for operating an engine configuredto use a plurality of differing fuels, the method comprising: monitoringa plurality of engine parameters; determining a fuel combustion ratio ofthe plurality of differing fuels associated with at least one enginecylinder of the engine based at least in part on one or more monitoredengine parameters and one or more of a plurality of characteristicprofiles along a defined path of a mobile asset in which the engine isdisposed, wherein the fuel combustion ratio comprises a ratio of theplurality of differing fuels to be delivered to the at least one enginecylinder, and the plurality of characteristic profiles comprises one ormore of global positioning sensor (GPS) information for a currentlocation of the mobile asset, a calculated distance from the currentlocation of the mobile asset to a fuel station, a fuel cost for one ormore of the plurality of differing fuels, a terrain profile associatedwith a location on the defined path, or an ambient temperature orambient pressure proximate to the mobile asset; and controlling a fueldelivery system to deliver the plurality of fuels to the at least oneengine cylinder based on the determined fuel combustion ratio.
 6. Themethod of claim 5, wherein one of the one or more monitored engineparameters comprises an increased load operation of the engine.
 7. Themethod of claim 6, wherein the increased load operation comprises atransient acceleration operation.
 8. The method of claim 6, furthercomprising determining if an increased load operation corresponds to anincreased gradient of the defined path at the current location of themobile asset.
 9. The method of claim 8, further comprising determiningin advance that an increased gradient is coming up along the definedpath and pre-staging the engine to anticipate the increased load. 10.The method of claim 9, wherein the pre-staging includes switchinghardware configurations comprising one of a valve event, compressionratio, piston, piston ring, valve lift profile, pressure sensor,temperature sensor, knock sensor, injector, or injector nozzle.
 11. Themethod of claim 9, wherein one of the one or more monitored engineparameters comprises an aftertreatment status.
 12. The method of claim6, wherein one of the one or more monitored engine parameters comprisesa sensor status for a temperature sensor or a knock sensor.
 13. Themethod of claim 6, wherein one of the one or more monitored engineparameters comprises increased engine speed.
 14. A fuel system,comprising: a fuel controlling unit configured to deliver a plurality ofdiffering fuels to at least one engine cylinder of an engine based atleast in part on a fuel combustion ratio, wherein the fuel combustionratio comprises a ratio of the plurality of differing fuels to bedelivered to the at least one engine cylinder and is based at least inpart on one or more of a plurality of characteristic profiles along adefined path of a mobile asset in which the engine is disposed, whereinthe fuel combustion ratio comprises a ratio of the plurality ofdiffering fuels to be delivered to the at least one engine cylinder, andthe plurality of characteristic profiles comprises one or more of globalpositioning sensor (GPS) information for a current location of themobile asset, a calculated distance from the current location of themobile asset to a fuel station, a fuel cost for one or more of theplurality of differing fuels, a terrain profile associated with alocation on the defined path, or an ambient temperature or ambientpressure proximate to the mobile asset.
 15. The system of claim 14,further comprising one or more sensors operable to communicate sensorinformation with the fuel controlling unit sensor information, and thefuel controlling unit is operable to receive the sensor information andthereby to determine the one or more of the plurality of characteristicprofiles.
 16. The system of claim 14, wherein the fuel controlling unitis configured to signal a fuel demand to a regasification unit to supplyat least one of the plurality of fuels.
 17. The system of claim 14,wherein the fuel controlling unit is configured to maintain an actualquantity of at least one of the plurality of differing fuels in themobile asset to less than or equal to a defined threshold quantity forthat fuel.
 18. The system of claim 14, wherein the plurality ofcharacteristic profiles further comprises one or more of historicaloperational data or ambient conditions along the defined path.
 19. Thesystem of claim 14, wherein the mobile asset in which the engine isdisposed is a vehicle.
 20. The system of claim 19, wherein the vehicleis a rail vehicle, and the plurality of differing fuels include dieseland natural gas.